The knob-tipped knife, a novel instrument utilizing a 2mm or 1.5mm cutting knife, is usually used for endoscopic submucosal dissection (ESD). Its knob-shaped tip and nonadjustable length make the knife less likely to slip and penetrate the tissue during the resection. Since the process of precut papillotomy is similar to ESD, the precutting procedure with the knob-tipped knife may be easier to be performed, as well as be safer. The efficacy and safety of this instrument in precut papillotomy have not been reported. We therefore assessed the efficacy and safety of the knob-tipped knife in precut papillotomy in difficult CBD cannulation.